Cancer incidence among Canadian immigrants, 1980-1998: results from a national cohort study.

Canadian immigrants have lower overall cancer risk than the Canadian-born population. Less is known about risks for immigrant subgroups and site-specific cancers. Linked administrative data sets were used to compare cancer incidence between subgroups of immigrants to Canada and the general Canadian population. The study involved 128,962 refugees and 241,010 non-refugees. Standardized incidence ratios (SIRs) were calculated for all-site and site-specific cancers by immigration categories and regions of birth. Relative to the general Canadian population, incidence of all-site cancer was lower among immigrants overall, by sex and refugee status (non-refugee SIRs 0.25: men, 0.24: women; refugee SIRs 0.31: both). Significantly higher SIRs resulted for liver, nasopharyngeal and cervical cancers, including liver cancer among South-East Asian and North-East Asian immigrants, and nasopharyngeal cancer among North-East Asian non-refugees. Hypothesized explanations for variation in cancer incidence include earlier viral infection in the country of origin.